1. Field of Invention
This application relates to supported activated catalyst compositions and methods of forming supported activated catalyst compositions using fluorine-modified supports.
2. Description of Related Art
As reflected in the patent literature, a great deal of effort has been expended towards discovering improvements in polymerization processes. For many polymerization processes, supported catalysts are required, and various methods of attaching metallocene catalysts to a support are known in the art. Supports suitable for use with metallocene catalyst are generally porous materials and can include organic materials, inorganic materials and inorganic oxides.
However, many supports contain reactive functionalities. In some instances, these reactive functionalities may deactivate or reduce the activity of the catalyst fixed to the support. When this occurs, the addition of more catalyst to the catalyst system may be necessary to ensure sufficient polymer production during olefin polymerization. Increasing the catalyst concentration in the catalyst system to compensate for activity reduction caused by reactive functionalities has various shortcomings. For instance, the addition of more catalyst may also require the addition of more activator. As such, increasing the concentrations of both catalyst and activator to overcome the effects of catalyst deactivation by reactive functionalities may substantially increase the cost of olefin polymerization.
Hydroxyl groups are an example of a reactive functionality present on some supports, which tend to deactivate metallocene catalysts. Hydroxyl groups are present on supports, such as inorganic oxides. An example of an inorganic oxide is silica gel. As such, when using silica gel to support a metallocene catalyst, it is desirable to remove, reduce or render inactive a sufficient number of the hydroxyl groups, wherein the sufficient number may be any excess hydroxyl groups that are not going to be exchanged with an activator in subsequent processes. Methods of removing or reducing the number of hydroxyl groups include thermal and/or chemical treatments.
Thermally treating or heating the support material generally avoids contamination of the support by undesirable chemicals. However, in the case of many porous supports, such as silica gel, heating the support may fail to achieve sufficient dehydroxylation. Chemically treating the support material can be expensive and may result in contamination of the support.
Thus, there remains a need for providing supported metallocene catalyst systems with high activity. Particularly, there remains a need for improved supported metallocene catalysts wherein the reactive functionalities of the support are reduced and/or deactivated.